493 publications from this institution
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A nondestructive observation of oxidationinduced stacking faults (OSF) generated during thermal oxidation processes in silicon has been carried out by using a scanning photoacoustic (PA) microscope. PA signals were detected with ZnO transducer fabricated on back surface of a sample. We found a good correlation between PA topoeraphs and etch-Dit distribution due to OSF a I-. near the sample surface. about 70 um in the present PA microscope. In order to make a quantitative evaluation of surface recombination velocity and temperature rise of a Si sample, the Jackson-Amer model was extended to take account of intraband relaxation and diffusion of excess carriers and nonradiative recombination at surface and in bulk. We found the larger surface recombination velocity and the higher temperature rise in the vicinity of defects (OSF) near the surface of Si. Spatial resolution was
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We have developed a new photothermalradiation (PTR) microscope for noncontact and nondestructive evaluation of defects in semiconductors. Thermal radiation from local heating area was detected with a HgCdTe infrared detector which is highly sensitive to the radiation in the wavelength range from 8 to 13 pm. We measured a PTR topograph and a photoluminescence (PL) topograph of a GaAs wafer. We found that the PTR signal increases remarkably at a surface damage on the GaAs wafer where the PL intensity decreases. We also measured PTR topographs of a thermally oxidized Si wafer. It is found that peaks of the PTR topograph correspond to small defects on the oxide films. We found an unexpected result that the PTR signal decreases at a deep scratch in contrast to the increase of the PA signal reported previously. We pointed out that the thermal emissivity of the sample surface is a very important factor for a detailed analysis of the PTR topograph.
Analytical study on cracking behavior of concrete due to rebar corrosion in the cases of multi-rebar specimens with various rebar spacings, of specimens with locally corroded rebar and specimens with pitting corrosion rebar was carried out. Three-dimensional Rigid-Body-Spring-Method (RBSM) with three phase material corrosion expansion model was applied to simulate crack initiation, internal cracking patterns and crack width propagation. It was confirmed that rebar spacing, ratio of local corrosion length and rebar length and pitting corrosion pattern played important roles in the cracking behavior.
実物大 PHC杭に対して，これまで行われてこなかった地震時の地盤変位を考慮した逆対称曲げモーメント分布となる載荷方式で，直接引張および低圧縮軸力を作用させた実験を，正負交番載荷を含め行った．また，ひび割れのような不連続現象を直接的に評価可能な剛体バネモデル（RBSM）を用いてPHC杭をモデル化し，その適用性を実験との比較で確認した．そして，その解析手法による数値実験を行うことで，軸力，せん断スパン比，杭径（径厚比），らせん鉄筋，繰返し変位振幅が終局せん断耐力に及ぼす影響を考察した．実験および解析結果から，対象としたPHC杭は，最大耐力まで十分な軸力保持性能を有し，軸力によるせん断耐力の変化が既往設計式より大きくなること，引張や低圧縮軸力下では安全裕度が小さくなる可能性があることが示された．
